The invention relates generally to polyphase linear motors and more particularly to line reactors unitarily housed with linear-motor stators.
Linear induction motors and other linear motors are often configured as polyphase motors, usually with three phases. Because of magnetic end effects and winding layouts, the inductances of the stator windings typically differ from phase to phase. The stator phases should be excited by currents nearly equal in magnitude so that an optimal traveling magnetic flux wave is generated. The current imbalance in stators resulting from unequal phase inductances is solved in two main ways. One solution is to drive the stator coils with a current-regulated amplifier, but current-regulated drives are expensive. Another way stator inductances are balanced is with inductive reactors. Inductor coils in the reactors are connected in series with the stator windings to balance the net inductances of the phases so that the stator can be driven by a more common variable-frequency drive (VFD). Because the reactors are separate units external to the stators, they must be packaged with and electrically connected to the stator. The packaging and the cabling can be difficult in harsh environments, such as those requiring NEMA 4X or IP67 washdown ratings.